Network your way in (Europe edition)

First of all a huge thank you for the WSO community!
I´m currenty a 1st year Bachelor student at an european target (SSE/Bocconi/HEC). And secured an summer analyst gig at a small M&A boutique (using my self-taught modelling skills). Next year, I plan on applying to some tier 1/2 PE and IB´s. HOWEVER, I have a huge disadvantage. I might end up with below average grades...

Can networking and my experience compensate for my grades? If yes, how should I do it? I know that the founder of a tier 2 boutique (Lincoln/Baird/Jeffries) used to be a professor at my school.
Is it a good idea to contact him?
Also, when should I start networking?
Who should I contact, former interns, Analysts or even Associates and VP´s?
My internship goes for 10 weeks and being in the financial center of my country its relatively easy to meet up with professionals from the industry (btw is it expected that I pay for the coffee?) but how do I contact with people from london (obviously they should be from the same school or speak the same language) but its not possible to meet up for a coffee?
Probably the most important question is wheter I should focus on employees from banks or from boutiques, does it make a difference? (e.g. is it even possible at banks to get invited to an interview just because I got recommended from an employee?)

I know this seems basic, but being a first year student from a not privileged background I don´t really have a clue regarding networking and how to behave.